WO2017149965A1 - Récepteur, émetteur, et procédé de décodage de signal - Google Patents

Récepteur, émetteur, et procédé de décodage de signal Download PDF

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WO2017149965A1
WO2017149965A1 PCT/JP2017/001456 JP2017001456W WO2017149965A1 WO 2017149965 A1 WO2017149965 A1 WO 2017149965A1 JP 2017001456 W JP2017001456 W JP 2017001456W WO 2017149965 A1 WO2017149965 A1 WO 2017149965A1
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unit
frequency
data
signal
fourier transform
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Japanese (ja)
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正裕 青野
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Hitachi Ltd
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Hitachi Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes

Definitions

  • the present invention relates to a receiver, a transmitter, and a signal decoding method.
  • orthogonal frequency division multiplexing In conventional cellular phone communication, digital modulation of orthogonal frequency division multiplexing may be employed.
  • This orthogonal frequency division multiplexing is multicarrier modulation in which data is carried on a number of subcarriers. Since these subcarriers are orthogonal to each other, they do not interfere with each other even though there is an overlap on the frequency axis, and each subcarrier can be distinguished by fast Fourier transform processing.
  • Patent Document 1 states that “a 2N-channel baseband pulse amplitude modulation signal synchronized with each other with a clock period of T seconds, a frequency difference between adjacent carriers is 1 / T cycle, and carriers are in phase or quadrature with each other.
  • a quadrature multiplexed signal transmission / reception system in which N is converted to N quadrature amplitude modulation signals by 2N carriers whose phases are set so as to maintain the same, and then these signals are multiplexed and transmitted, two in-phase channels adjacent to each other in the frequency domain And at the identification time of each baseband signal demodulated at the receiving side by giving a delay difference of T / 2 seconds between the transmitting side baseband pulse amplitude modulation signals corresponding to these two orthogonal channels only.
  • Transmission and reception of orthogonal multiplexed signals characterized by almost zero intersymbol interference and interchannel interference It has been described as expressions ".
  • Patent Document 1 describes a method of performing frequency multiplex communication using a plurality of orthogonal carrier waves. However, this method limits the frequency utilization efficiency and limits the communication speed of wireless communication. Therefore, an object of the present invention is to provide a receiver, a transmitter, and a signal decoding method that can improve the frequency utilization efficiency and improve the communication speed of wireless communication.
  • the receiver of the present invention receives a signal that is modulated with transmission data at a modulation speed equal to or higher than the predetermined frequency for each of a plurality of subcarriers that differ by a predetermined frequency.
  • a Fourier transform calculation unit that performs a discrete Fourier transform on the output signal of the reception unit, the frequency after conversion being limited to the frequency of the subcarrier, and reception from each subcarrier calculated by the Fourier transform calculation unit
  • a data acquisition unit for acquiring data Other means will be described in the embodiment for carrying out the invention.
  • 1st Embodiment is an example of the radio equipment provided with the receiver which performs the Fourier transformation which restrict
  • FIG. 1 shows the configuration of the transmitter 1.
  • the transmitter 1 includes a transmission signal generation unit 11, a D / A converter (Digital Analog Converter) 12, and a radio frequency (RF) circuit 13, and a transmission antenna 10 is connected thereto.
  • the transmission signal generated by the transmission signal generation unit 11 is converted into an analog signal by the D / A converter 12.
  • This analog signal is amplified by the high frequency circuit 13 and band-limited, and transmitted from the transmitting antenna 10.
  • the D / A converter 12 and the high frequency circuit 13 are transmission units that transmit the output of the transmission signal generation unit 11 as a signal.
  • FIG. 2 shows a configuration of the transmission signal generation unit 11.
  • the transmission signal generation unit 11 includes a first carrier wave generation unit 14a to a fifth carrier wave generation unit 14e, a first carrier wave modulation unit 15a to a fifth carrier wave modulation unit 15e, a transmission data generation unit 16, and a transmission data parallelization unit 17 And an adder 18 and a transmission signal normalization unit 19.
  • the data to be transmitted to the receiver is generated by the transmission data generation unit 16.
  • the generated data is parallelized by the transmission data parallelization unit 17 into five pieces equal to the number of subcarriers.
  • the five pieces of parallel data are simultaneously transmitted using the frequency multiplexing communication method. Note that the number of subcarriers is not limited to five, and may be any natural number n.
  • a sine wave is generated as a digital signal.
  • Each carrier generation unit is required by the number of subcarriers to be used.
  • the first carrier wave generation unit 14a generates a sine wave having a frequency (f c + f b ).
  • the second carrier wave generation unit 14b generates a sine wave having a frequency (f c + f b ⁇ 2).
  • the third carrier wave generation unit 14c generates a sine wave having a frequency (f c + f b ⁇ 3).
  • the fourth carrier wave generation unit 14d generates a sine wave having a frequency (f c + f b ⁇ 4).
  • the fifth carrier wave generation unit 14e generates a sine wave having a frequency (f c + f b ⁇ 5). Each generated sine wave is modulated by the first carrier modulation unit 15a to the fifth carrier modulation unit 15e, respectively.
  • Each carrier modulation unit is required as many as the number of subcarriers to be used in the same manner as the carrier generation unit.
  • data parallelized by the transmission data parallelization unit 17 is used.
  • the modulated five carrier waves are added by the adder 18 and then normalized by the transmission signal normalization unit 19 and output. Normalization is signal processing that amplifies and attenuates a signal so that the amplitude of the output signal is kept constant.
  • FIG. 3 shows the configuration of the receiver 2.
  • the receiver 2 includes a high frequency circuit 22, an A / D converter (Analog Digital Converter) 23, a Fourier transform calculation unit 24, and a data acquisition unit 25 connected to the reception antenna 21.
  • a reception signal received by the reception antenna 21 via the wireless communication path is amplified and band-limited by the high frequency circuit 22 and converted into a digital signal by the A / D converter 23.
  • This digital signal is Fourier-transformed by the Fourier transform calculation unit 24 and becomes reception data by the data acquisition unit 25.
  • Fourier transform is performed by limiting the frequency after the transform.
  • the reception antenna 21, the high frequency circuit 22, and the A / D converter 23 receive a signal that is modulated at a modulation speed equal to or higher than a predetermined frequency by transmission data for each of a plurality of subcarriers that differ by a predetermined frequency.
  • the Fourier transform calculation unit 24 performs a discrete Fourier transform on the output signal of the reception unit in which the frequency after conversion is limited to the frequency of the subcarrier.
  • the data acquisition unit 25 acquires reception data from each subcarrier calculated by the Fourier transform calculation unit 24.
  • Equation (1) Each of the following equations shows a transmission signal with a limited frequency.
  • the transmission signal be f (t).
  • the transmission signal f (t) is the sum of subcarriers used for transmission, as shown in Equation (1).
  • D 0 is a constant component. Ideally, there are no constant components, but they are included in equation (1) to increase the accuracy of the Fourier transform.
  • a sine wave of phase ⁇ k can be separated into a sine wave and a cosine wave with no phase difference.
  • the transmission signal f (t) is expressed by Equation (2).
  • Sine and cosine waves can be represented by complex exponential functions.
  • the transmission signal can be expressed as in Expression (3).
  • C k is defined as in equation (4).
  • E k (t) is defined as in equation (5).
  • the transmission signal can be expressed as equation (6).
  • Expression (6) When Expression (6) is converted, it can be expressed as Expression (7).
  • This is a Fourier transform calculation method in which the frequency after conversion is limited.
  • the received signal needs to be sampled over (2n + 1) points, and the sampling points are (t k, v k ) (where ⁇ n ⁇ k ⁇ n).
  • v k is the value of the sampled signal.
  • a Fourier transform matrix M is defined as in equation (8). This matrix M depends only on the time of the sampling point, and if the time is determined, the matrix M can be uniquely determined.
  • a column vector of C k is defined as C as shown in Equation (9).
  • a column vector of v k is defined as V as shown in Expression (10).
  • Equation (11) Since the received signal is Equation (7), Equation (11) is established.
  • the Fourier transform matrix M exists the inverse matrix M -1.
  • the equation (12) is obtained. That is, the column vector C can be obtained from the sampling points by calculating the inverse matrix of M.
  • Equation (3) the following Equation (15) can be derived. That is, the amplitude D k of each subcarrier can be obtained.
  • the data acquisition unit 25 can acquire data from the amplitude D k of each subcarrier.
  • the following equation (16) can be derived. That is, the phase ⁇ k of each subcarrier can be obtained.
  • the data acquisition unit 25 can acquire data from the phase ⁇ k of each subcarrier.
  • the modulation method is on-off keying (OOK)
  • f c 920 MHz
  • f b 15 kHz
  • n 5
  • the modulation speed for each carrier is 50 kbps
  • the resolution of the A / D converter 23 is In the case of 12 bits, the transmission speed is 250 kbps.
  • FIG. 4 shows the configuration of the transmission signal generation unit 11 under the above-described conditions.
  • the transmission signal generation unit 11 includes switches 151a to 151e that function as the first carrier modulation unit 15a to the fifth carrier modulation unit 15e, and is otherwise configured in the same manner as the transmission signal generation unit 11 shown in FIG. Yes.
  • the transmission data generation unit 16 generates data to be transmitted to the receiver 2 (see FIG. 3).
  • the generated data is parallelized by the transmission data parallelization unit 17 into five pieces equal to the number of subcarriers.
  • the five pieces of parallel data are simultaneously transmitted using the frequency multiplexing communication method. Since five subcarriers are used and each carrier is modulated by 1 bit, the transmission data parallelization unit 17 converts the transmission data into 5-bit parallel data.
  • the transmission data parallelization unit 17 parallelizes the data so as to avoid only zero data. Note that the number of subcarriers is not limited to five, and may be any natural number n.
  • a sine wave is generated as a digital signal.
  • the first carrier generation unit 14a generates a carrier of 920.015 MHz.
  • Each generated sine wave is modulated by switches 151a to 151e, which are carrier wave modulation units.
  • the carrier wave is modulated by turning on the corresponding switch when the data is “1” and turning off the corresponding switch when the data is “0”.
  • the five modulated carrier waves are added by the adder 18 and then normalized by the transmission signal normalization unit 19 and output.
  • the output amplitude is normalized to 1. For example, when all the switches 151a to 151e are ON, the signal is set to 1/5, and when only 3 are set, the signal is set to 1/3.
  • the modulation speed is 50 kHz
  • the modulation period is 20 ms
  • the sampling frequency is 550 kHz.
  • the data acquisition unit 25 determines a threshold value, and obtains a received signal assuming that the subcarrier amplitude D k is greater than or equal to the threshold value is “1”, and that below the threshold value is “0”. When all the five carriers are “1”, D k is about 0.2, so that the received data can be suitably obtained when the threshold is 0.1 to 0.15.
  • FIG. 5 shows a simulation result of Fourier transform in which the frequency after conversion is limited. For each of the five subcarriers, the value of the amplitude D k is shown. The data related to the first, second, and fifth subcarriers is received as “1”, and the data related to the third and fourth subcarriers is received as “0”. As shown in FIG. 5, the frequency difference between the subcarriers is smaller than the frequency at which the subcarriers are orthogonal to each other. In this simulation, the bit error rate was 10 ⁇ 6 or less.
  • FIG. 6 shows a simulation result when the received signal having the above-described condition is subjected to Fourier transform by normal FFT (Fast Fourier Transform).
  • FFT Fast Fourier Transform
  • the use efficiency of the frequency can be improved by using the wireless device including the receiver 2 that performs the Fourier transform in which the frequency after the conversion in the first embodiment is limited.
  • the matrix is low-dimensional compared to normal FFT, the received wave can be demodulated from short-time sampling data.
  • the fundamental frequency becomes the frequency resolution, a high frequency resolution can be realized by fixing the fundamental frequency in advance.
  • the transmitter and receiver of the first embodiment are suitable for a large capacity wireless communication system of several Mbps inside a substation, a wireless communication system for a factory, a traffic system, a short-range wireless communication system, and the like.
  • FIG. 7 shows the configuration of the transmitter 1A.
  • This analog signal is multiplied by the carrier wave generated by the oscillator 32 in the high frequency circuit 13, amplified and band-limited by the high frequency circuit 13, and then transmitted from the transmission antenna 10.
  • the operating frequency of the D / A converter 12 can be lowered. Therefore, an inexpensive one can be used for the D / A converter 12.
  • FIG. 8 shows a carrier modulation unit when phase modulation (Phase Shift Keying, PSK) is used.
  • a first carrier modulation unit 15a (see FIG. 2) is realized by a combination of the inverter 152a and the switch 153a. The same applies to the inverters 152b to 152e and the switches 153b to 153e.
  • the switch 153a When the data is “1”, the switch 153a outputs the carrier wave as it is, and when the data is “0”, the inverter 152a outputs the carrier wave whose phase is shifted by 180 degrees. As a result, the amplitude of the transmission signal does not change, so signal normalization is not necessary.
  • the receiver 2 of the first embodiment uses the amplitude D k as received data.
  • the receiver 2A of the second embodiment uses the phase ⁇ k .
  • the sampling time t k is relative, inversion of “1” and “0” can occur. Therefore, a method of determining “1” and “0” using a pilot signal before communication, time synchronization between the transmitter 1A and the receiver 2A, and a sampling point time t k as an absolute time. It is necessary to use the method to do.
  • each of the amplitude D k and the phase ⁇ k takes four values.
  • the data acquisition unit 25 needs to set a threshold value for each to obtain data. As described above, it is possible to simplify the circuit and improve the communication speed by using the modulation method of the second embodiment.
  • FIG. 9 shows the configuration of the receiver 2A.
  • a carrier wave is reproduced by the carrier wave reproduction circuit 26 from the reception signal output from the high frequency circuit 22.
  • the reproduced carrier wave and the received signal are multiplied by a multiplier 27, filtered by a low-pass filter 28, and down-converted. It is possible to use a detection circuit instead of the carrier wave recovery circuit 26.
  • the sampling rate is 550 kHz. This is the minimum sampling rate for performing the Fourier transform.
  • this sampling rate is doubled, the sampling points are also doubled, and received data can be obtained using two different sets of data. By obtaining and averaging a plurality of received data, communication with few errors can be performed.
  • FIG. 10 is a flowchart of processing for determining the sampling rate.
  • the receiver 2A sets the smallest value as the initial value of the sampling frequency (step S10).
  • the receiver 2A sets a variable f to 0 (step S11), and then transmits a pilot signal transmission start request to the transmitter 1A (step S12).
  • the receiver 2A receives the pilot signal (step S13) and calculates a bit error rate (BER) (step S14). If the bit error rate satisfies the regulation (step S15 ⁇ Yes), after substituting the sampling frequency into the variable f (step S16), the sampling frequency is lowered by one step (step S17), and the process of step S13 is performed. Return to.
  • step S15 If the bit error rate does not satisfy the regulation (step S15 ⁇ No), it is determined whether the variable f is 0 or not. If the variable f is 0 (step S18 ⁇ Yes), the sampling frequency is increased by one level (step S19), and the process returns to step S13.
  • step S18 If the variable f is not 0 (step S18 ⁇ No), a sampling frequency at which the pit error rate satisfies the regulation has been found.
  • the receiver 2A transmits a pilot signal transmission stop request to the transmitter 1A (step S20), sets the sampling frequency (sampling speed) to the value of the variable f, and ends the flowchart of FIG. Thereafter, the A / D converter 23 samples the signal at the frequency f and demodulates it into a digital signal.
  • the number of carrier waves and the frequency difference can be made variable.
  • the processing for determining the sampling rate shown in FIG. 10 may be performed only once before the session is established, or may be performed depending on the communication situation such as when the communication error rate deteriorates. According to the processing for determining the sampling rate of this embodiment, it is possible to select a sampling rate according to the communication environment.
  • the present invention is not limited to the embodiments described above, and includes various modifications.
  • the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described.
  • a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment.
  • control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other. Examples of modifications of the present invention include the following (a) to (e).
  • (A) The communication path between the transmitter and the receiver is not limited to wireless, but may be wired. Application examples may be digital television, broadcasting, broadband internet connection, and the like. According to the present invention, since clock synchronization is not necessary, data communication can be speeded up.
  • B The number of subcarriers is not limited to five.
  • Subcarrier modulation is not limited to 1-bit modulation of transmission data, and multi-level modulation such as 256QAM (256 Quadrature Amplitude Modulation) may be used. As a result, the data communication can be further speeded up.
  • the sampling frequency adjustment process is not limited to the process according to the flowchart of FIG.
  • the transmission wave may be calculated by directly adding and subtracting each carrier wave without being limited to the inverse Fourier transform.

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

La présente invention concerne l'amélioration de l'efficacité de l'utilisation de fréquence et l'augmentation de la vitesse de communication d'une communication sans fil. Un récepteur (2) est fourni avec : une unité de réception qui reçoit un signal obtenu par modulation de chacune d'une pluralité de sous-porteuses qui diffère par une fréquence prédéterminée avec des données de transmission à une vitesse de modulation supérieure ou égale à une fréquence prédéterminée ; une unité de calcul de la transformée de Fourier (24) qui, par rapport au signal de sortie émanant de l'unité de réception, réalise une transformée de Fourier discrète dans laquelle les fréquences après transformation sont limitées aux fréquences des sous-porteuses ; et une unité d'acquisition de données (25) qui acquiert des données de réception depuis chacune des sous-porteuses calculées par l'unité de calcul de la transformée de Fourier (24).
PCT/JP2017/001456 2016-03-01 2017-01-18 Récepteur, émetteur, et procédé de décodage de signal Ceased WO2017149965A1 (fr)

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JP2016-039033 2016-03-01

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010093697A (ja) * 2008-10-10 2010-04-22 Fujitsu Ltd マルチキャリア無線送信装置
JP2013126030A (ja) * 2011-12-13 2013-06-24 National Institute Of Advanced Industrial & Technology スペクトル拡散通信システム
JP2015164257A (ja) * 2014-02-28 2015-09-10 株式会社Ｎｔｔドコモ 無線基地局、ユーザ端末、無線通信方法及び無線通信システム

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010093697A (ja) * 2008-10-10 2010-04-22 Fujitsu Ltd マルチキャリア無線送信装置
JP2013126030A (ja) * 2011-12-13 2013-06-24 National Institute Of Advanced Industrial & Technology スペクトル拡散通信システム
JP2015164257A (ja) * 2014-02-28 2015-09-10 株式会社Ｎｔｔドコモ 無線基地局、ユーザ端末、無線通信方法及び無線通信システム

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